much. when the quake hit they were turned off. what those three reactors have, the reason we are talking about them now is because they have spent fuel pools inside them. as far as we can tell, they are just protected by outer containment walls. we've had two fires and an explosion at one of the reactors with spent fuel pool in it. we've had reports of the water level dropping at two other spent fuel pools. these are the spent fuel pools at fukushima. there is trouble there keeping them cool, and there is a danger because of it. at reactor 4, there has been an explosion and there have now been two fires. we know that an explosion there cracked the roof. it appears that damage to the spent fuel rods is what is allowing for a release of radioactivity there. japanese authorities did report a large spike in radio activity after the fire in number 4. what that means is that either the force of that explosion or smoke from the fire or both carried aloft the radioactive